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Electron and hole drift velocity in chemical vapor deposition diamond
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Element Six Ltd, Ascot Berkshire, UK.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2011 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 6, 063719- p.Article in journal (Refereed) Published
Abstract [en]

The time-of-flight technique has been used to measure the drift velocities for electrons and holes in high-purity single-crystalline CVD diamond. Measurements were made in the temperature interval 83 ≤ T ≤ 460 K and for electric fields between 90 and 4 × 103 V/cm, applied in the <100> crystallographic direction. The study includes low-field drift mobilities and is performed in the low-injection regime to perturb the applied electric field only minimally.

Place, publisher, year, edition, pages
2011. Vol. 109, no 6, 063719- p.
Keyword [en]
velocity, time-of-flight, carrier drift mobility, single crystal diamond
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics; Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-122792DOI: 10.1063/1.3554721ISI: 000289149900072OAI: oai:DiVA.org:uu-122792DiVA: diva2:311066
Funder
Swedish Research Council
Available from: 2011-04-09 Created: 2010-04-20 Last updated: 2012-08-01Bibliographically approved
In thesis
1. Charge Transport in Single-crystalline CVD Diamond
Open this publication in new window or tab >>Charge Transport in Single-crystalline CVD Diamond
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a semiconductor with many superior material properties such as high breakdown field, high saturation velocity, high carrier mobilities and the highest thermal conductivity of all materials. These extreme properties, as compared to other (wide bandgap) semiconductors, make it desirable to develop single-crystalline epitaxial diamond films for electronic device and detector applications. Future diamond devices, such as power diodes, photoconductive switches and high-frequency field effect transistors, could in principle deliver outstanding performance due to diamond's excellent intrinsic properties. However, such electronic applications put severe demands on the crystalline quality of the material.

Many fundamental electronic properties of diamond are still poorly understood, which severely holds back diamond-based electronic device and detector development. This problem is largely due to incomplete knowledge of the defects in the material and due to a lack of understanding of how these defects influence transport properties.

Since diamond lacks a shallow dopant that is fully thermally activated at room temperature, the conventional silicon semiconductor technology cannot be transferred to diamond devices; instead, new concepts have to be developed. Some of the more promising device concepts contain thin delta-doped layers with a very high dopant concentration, which are fully activated in conjunction with undoped (intrinsic) layers where charges are transported. Thus, it is crucial to better understand transport in high-quality undoped layers with high carrier mobilities.

The focus of this doctoral thesis is therefore the study of charge transport and related electronic properties of single-crystalline plasma-deposited (SC-CVD) diamond samples, in order to improve knowledge on charge creation and transport mechanisms. Fundamental characteristics such as drift mobilities, compensation ratios and average pair-creation energy were measured. Comparing them with theoretical predictions from simulations allows for verification of these models and improvement of the diamond deposition process.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 746
Keyword
CVD diamond, wide-bandgap semiconductor, single-crystalline diamond, carrier transport, time-of-flight, drift velocity, mobility, compensation, pair-creation, electronic devices, diamond detector, diamond diode
Identifiers
urn:nbn:se:uu:diva-122794 (URN)978-91-554-7815-5 (ISBN)
Public defence
2010-06-04, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2010-05-12 Created: 2010-04-20 Last updated: 2010-05-18Bibliographically approved
2. Experimental Studies of Charge Transport in Single Crystal Diamond Devices
Open this publication in new window or tab >>Experimental Studies of Charge Transport in Single Crystal Diamond Devices
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a promising material for high-power, high-frequency and high- temperature electronics applications, where its outstanding physical properties can be fully exploited. It exhibits an extremely high bandgap, very high carrier mobilities, high breakdown field strength, and the highest thermal conductivity of any wide bandgap material. It is therefore an outstanding candidate for the fastest switching, the highest power density, and the most efficient electronic devices obtainable, with applications in the RF power, automotive and aerospace industries. Lightweight diamond devices, capable of high temperature operation in harsh environments, could also be used in radiation detectors and particle physics applications where no other semiconductor devices would survive.

The high defect and impurity concentration in natural diamond or high-pressure-high-temperature (HPHT) diamond substrates has made it difficult to obtain reliable results when studying the electronic properties of diamond. However, progress in the growth of high purity Single Crystal Chemical Vapor Deposited (SC-CVD) diamond has opened the perspective of applications under such extreme conditions based on this type of synthetic diamond.

Despite the improvements, there are still many open questions. This work will focus on the electrical characterization of SC-CVD diamond by different measurement techniques such as internal photo-emission, I-V, C-V, Hall measurements and in particular, Time-of-Flight (ToF) carrier drift velocity measurements. With these mentioned techniques, some important properties of diamond such as drift mobilities, lateral carrier transit velocities, compensation ratio and Schottky barrier heights have been investigated. Low compensation ratios (ND/NA) < 10-4 have been achieved in boron-doped diamond and a drift mobility of about 860 cm2/Vs for the hole transit near the surface in a lateral ToF configuration could be measured. The carrier drift velocity was studied for electrons and holes at the temperature interval of 80-460 K. The study is performed in the low-injection regime and includes low-field drift mobilities. The hole mobility was further investigated at low temperatures (10-80 K) and as expected a very high mobility was observed.

In the case of electrons, a negative differential mobility was seen in the temperature interval of 100-150K. An explanation for this phenomenon is given by the intervally scattering and the relation between hot and cold conduction band valleys. This was observed in direct bandgap semiconductors with non-equivalent valleys such as GaAs but has not been seen in diamond before.

Furthermore, first steps have been taken to utilize diamond for infrared (IR) radiation detection. To understand the fundamentals of the thermal response of diamond, Temperature Coefficient of Resistance (TCR) measurements were performed on diamond Schottky diodes which are a candidate for high temperature sensors. As a result, very high TCR values in combination with a low noise constant (K1/f) was observed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 944
Keyword
Single crystal diamond, carrier transport, CVD diamond, time-of-flight, mobility, IR detector, compensation, diamond diode, drift velocity, thermal detector
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-173599 (URN)978-91-554-8391-3 (ISBN)
Public defence
2012-06-05, Häggsalen, Lägerhyddsvägen 1, Ångströmlaboratoriet, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2012-05-15 Created: 2012-05-01 Last updated: 2013-01-07Bibliographically approved

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